Modern commercially built aircraft have the majority of their structures constructed of a multitude of formed sheets of material, primarily aluminum. Generally, these sheets of material are assembled with one another by rivets. While other construction methods and materials are being developed and used commercially in the aerospace industry, the above method is likely used in the vast majority of aircraft construction, and in fact is used in some other industries also.
The above described construction method results in a relatively lightweight and sturdy structure, but when damage occurs to such a structure the accepted procedure in the aerospace industry is to completely remove the damaged components or material and replace them with new, undamaged material rather than attempting to straighten or otherwise repair the damaged components. In order to accomplish this, any rivets holding the damaged components in place must be removed. The Federal Aviation Administration (FAA) regulations require that acceptable standards and practices be used in the repair of aircraft to airworthy condition, as described in FAA Advisory Circular (AC) 43-13. AC 43-13 states that when removing rivets, the head should be weakened (but not entirely drilled through) with a drill bit of the same diameter as that of the rivet shank. A punch of the proper diameter is then inserted in the drilled hole in the rivet head and the head is snapped off, leaving the shank in the rivet hole. The rivet shank itself is not drilled out, as such a procedure would almost certainly widen or distort the rivet hole, thus requiring the extra step of redrilling the hole to the proper size for the next larger rivet size.
Standard practice for the removal of the rivet shank is to punch out the shank with a proper diameter punch. However, for relatively light weight structures formed of relatively thin sheet material, the back of the material must be supported in order to prevent the distortion of the sheet material due to the force used in driving out the rivet shank; this is especially true with relatively soft metals such as aluminum. This is commonly done with a rivet bucking bar or some other relatively massive object placed immediately adjacent the remaining "shop head" of the rivet shank, on the opposite side of the material from the "manufactured head" which was removed.
While the step of removing the manufactured rivet head is easily accomplished by a single person using the above procedure, it will be seen that at least two people are required for the step of removing the rivet shank. One person must hold the punch on the rivet shank while hammering the punch to drive out the rivet shank, while a second person must "back up" the sheet metal structure from the opposite side with a bucking bar or similar object in order to prevent distortion of the sheet metal material. Moreover, such work requires a skilled team, as the skills involved are closely related to the skills required when driving and bucking such rivets in the first place. If the person using the bucking bar does not precisely coordinate his or her efforts with the hammer blows of the person driving out the shank, the sheet material may be damaged in any case. Additionally, most bucking bars are formed with relatively straight edges, which means that the edge of such a bar will only support one side of the sheet material as the rivet shank is driven out, thus again raising the possibility of damage to the structure. Obviously, if such work is done carelessly, the repaired structure will not possess the strength of the original undamaged structure due to the possibility of elongated rivet holes and/or distorted sheet metal.
The need arises for a tool for driving out the shanks of rivets in such structures, which tool may be operated by a single person using only one hand. The tool must also provide proper support for the underlying surface as the rivet shank is driven therethrough, in order to prevent distortion of the material and/or rivet hole. Such a tool should be relatively simple in construction and operation and relatively inexpensive to purchase in order to provide the benefits of such a tool to the broadest possible number of users and thereby increase the likelihood of structurally sound repairs.